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Reimagining of Schrodinger's Cat Breaks Quantum Mechanics -- and Stumps Physicists (nature.com)
In a multi-'cat' experiment, the textbook interpretation of quantum theory seems to lead to contradictory pictures of reality, physicists claim. New submitter Lanodonal shares a report: In the world's most famous thought experiment, physicist Erwin Schrodinger described how a cat in a box could be in an uncertain predicament. The peculiar rules of quantum theory meant that it could be both dead and alive, until the box was opened and the cat's state measured. Now, two physicists have devised a modern version of the paradox by replacing the cat with a physicist doing experiments -- with shocking implications.
Quantum theory has a long history of thought experiments, and in most cases these are used to point to weaknesses in various interpretations of quantum mechanics. But the latest version, which involves multiple players, is unusual: it shows that if the standard interpretation of quantum mechanics is correct, then different experimenters can reach opposite conclusions about what the physicist in the box has measured. This means that quantum theory contradicts itself.
The conceptual experiment has been debated with gusto in physics circles for more than two years -- and has left most researchers stumped, even in a field accustomed to weird concepts. "I think this is a whole new level of weirdness," says Matthew Leifer, a theoretical physicist at Chapman University in Orange, California. The authors, Daniela Frauchiger and Renato Renner of the Swiss Federal Institute of Technology (ETH) in Zurich, posted their first version of the argument online in April 2016. The final paper [PDF] appears in Nature Communications on 18 September.
Quantum theory has a long history of thought experiments, and in most cases these are used to point to weaknesses in various interpretations of quantum mechanics. But the latest version, which involves multiple players, is unusual: it shows that if the standard interpretation of quantum mechanics is correct, then different experimenters can reach opposite conclusions about what the physicist in the box has measured. This means that quantum theory contradicts itself.
The conceptual experiment has been debated with gusto in physics circles for more than two years -- and has left most researchers stumped, even in a field accustomed to weird concepts. "I think this is a whole new level of weirdness," says Matthew Leifer, a theoretical physicist at Chapman University in Orange, California. The authors, Daniela Frauchiger and Renato Renner of the Swiss Federal Institute of Technology (ETH) in Zurich, posted their first version of the argument online in April 2016. The final paper [PDF] appears in Nature Communications on 18 September.
Schrodinger's Cat is just a thought experiment. The rules of quantum mechanics don't apply to large scale things like cats.
Applying Schrodinger's Cat to physics itself does not actually change physics.
I'm a good cook. I'm a fantastic eater. - Steven Brust
Fuck all MAGAtards!!
Is this just another way of saying "Number 7 will shock you!"
"I think I can safely say that nobody understands quantum mechanics."
A physicist in a superposition of feeder and food states until the refrigerator is opened?
Aren't the physicists in the box collapsing the function already by observing the coin? Unless we are saying that the system would behave like nested functions where the internal function collapses when the internal observation is made and a secondary function that includes the 1st one as a variable also collapses when the external observer performs their observation.
We replaced the cat with Folgers Crystals. Let’s see if anyone notices.
In the world's most famous thought experiment, physicist Erwin Schrodinger described how a cat in a box could be in an uncertain predicament.
Compared to the second most famous, but ironically similar: "Does this dress make me look fat?"
Where your relationship is also in an "uncertain predicament" -- being both dead and alive -- until the question is answered.
It must have been something you assimilated. . . .
I don’t think it’s possible to KNOW precisely at any given moment whether quantum mechanics is broken, and to what degree it IS broken if indeed it is. That’s kind of the point of quantum mechanics.
OR...
If a mechanic breaks your quantum, he should have to fix it, theoretically.
I cant decide which joke to go with, so I've decided on a quantum superposition of both:
If don’t mechanic it’s your to he preciesly have any fix...
Hehehehe... quantum humor... simultaneously both really funny, and not funny at all, but you won’t know WHICH it is unitl you read the joke and collapse the wave-function.
Our reign has gone on long enough. Indeed. Summon the meteors.
...but only if you believe in it, like Tinkerbell.
Finally the ultimate class separation, into those who can believe in magic and those who cannot.
"There is more worth loving than we have strength to love." - Brian Jay Stanley
I say we just leave the physicists in the box and go get a beer.
If the cat were dead, you'd be sure to smell it.
When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
I never understood how it should work when the cat is a conscious observer anyway.
Then know that being neither in or out -- Dead or alive helps.
I am not sure if I completely understood the paper but I think the problem is about so called coherences.
In quantum mechanics a particle can be half in spin up and half in spin down. But it can also be minus one half in spin up and plus one half in spin down. The negative sign stems from the quantum coherence. The probabilities for each case are still the same to find the particle in the respective state. It used to be thought that an observer of the particle could also be regarded to be in such a coherent state. And that it didn't matter that to him it didn't look like it, but for him it looked like nature had already decided on an outcome.
It turns out that this isn't the case. Either the quantum state was already collapsed by the observer or not. The views are incompatible and lead to disagreement. The paper constructs this explicit disagreement.
If scientists can't agree on this will it be a cat fight.
"That's the way to do it" - Punch
Most physicists don't give much credence to the Copenhagen Interpretation. There are better ways to think about quantum mechanics.
https://en.wikipedia.org/wiki/...
Everybody believes it will change the world, but nobody can show proof of how.
It is a cat.
When the cat wants to be in the box, it is in the box.
When it wants to be out of the box, it is out of the box.
Death of cats is expressly prohibited under the Rules of War.
Now, parrots or songbirds, those are ok.
-- Tigger warning: This post may contain tiggers! --
Schrödinger's point about the cat thought experiment is that that cat is NOT in two separate states at the same time. That was his expressing his aggravation about the contradiction of the results of his work and reality.
The question remains, "How does potential get resolved?"
They should call this the Xzibit Effect.
Because yo dawg, we heard you liked measuring the quantum state of experiments, so we put some experiments in your experiments so you could break the rules of quantum mechanics. I mean, so you could experiment while you experiment.
https://foundations.ethz.ch/wp-content/uploads/2018/04/renner.pdf
Schrödinger's Cat isn't science. It might be considered mathematics, logic, or philosophy, but science requires falsifiable predictions, and Schrödinger's Cat doesn't make any.
It would be neat if it can be logically disproven, though, then it would be science fiction.
Did they just find the Godelian loop of QED?
This just seems like a reiteration of the Many world interpretation?
https://en.wikipedia.org/wiki/...
So is this more scientists arguing about the 2&3 polarizing filter Bell's theorem example?
You know the one where 2 linear filters at 90 block a photon 100% of the time but if you add a third filter in between the two at 45 they all block the photon ~47% of the time?
Like is this a Local Realism thing?
Or is this more of a "what constitutes an observer" question?
... different experimenters can reach opposite conclusions about what the physicist in the box has measured.
Einstein introduced us to the fact that the universe can appear very different from different points of view. For example, if explosions of supernova "A" and supernova "B" occur, it may be observed that "A" occurred before "B", or that "B" occurred before "A", depending on where the observation was made. Either observation is equally valid, even though the conclusions are logically opposite.
Once one accepts the notion that physical observations are "relative", why is it so shocking that quantum mechanical observations might also be logically opposite, depending on who is observing?
Cats have 9 lives.
This is because making a "measurement" some magic processes that collapses a wave function is utter bullshit.
I thought the purpose of Schrodinger's cat thought experiment was to illustrate the absurdity of the Copenhagen interpretation. So, now the new thought experiment is again reinforcing original thought experiment... that you can have two different conclusions?
I have looked at the article's text. The key assumption, which I would say is bullshit, is on Page 3.
> Assumption (Q) is that any agent A "uses quantum theory."
We simply don't know if an agent, which is a quantum-mechanical system, can use quantum theory. I.e., whether the quantum theory contains a useful non-trivial model of the part of itself which is relevant to the experiment described in the article.
This indicates that quantum theory cannot be extrapolated to complex systems, at least not in a straightforward manner
So, coarse-graining still applies?
Your description would seem to favour the totally observer-subjective viewpoint. As the information converges (that is, more and more entangled things are measured together), there is a more and more constrained and complicated wavefunction, with many very particular peaks and valleys, and very rapidly less remaining uncertainty in state description.
But still, could there be two inconsistent versions of all that, held by so-far-not-entangled observers? When those observers finally compare notes, by convolving their models of what's out there together (becoming entngled), it's interesting that that comes out to a single consistent classical state estimation.
Or maybe it isn't interesting. Maybe it's just the way that math (convolution of wavefunctions) has to work, and whatever that says, that's what you get, and somehow "of course" that's a consistent description of classical reality.
Where are we going and why are we in a handbasket?
It seems to me that much of the 'weirdness' of quantum physics comes from the complexity of mathematics that are meant to allow for a possible range of unknown values (aka probability fields).
So, what I've never been able to understand is this. Just because we are unable to know both the position and speed of a particle, why is there an assumption made that the particle doesn't have both a position and speed?
I guess the point is it seems like most of the 'weirdness' stems from the assumption that the model is a complete and accurate description of reality.
Why do people assume that?
I'm not well educated on some of this but I'm trying to learn.
Thanks for patients ahead of time.
âoeTolerance applies only to persons, but never to truth. Intolerance applies only to truth, but never to persons.
Let me get this straight, when the box opens does the cat see Schrodinger alive or dead?
I mean, whatever contrived radio active decay a poison trigger nonsense the cat has to put up with also applies to Schrodinger.
Ahh, the old determinism debate - does God roll dice and if a tree falls in a forest does it make a sound?
Quantum mechanics (and thermodynamics for that matter) are useful mathematical models rooted in statistics. They are extremely useful tools but ultimately not exactly how our universe works. A true model that infallibly predicts all actions would need to take into consideration the state of all matter and energy in the entire universe. Obviously this is utterly impractical for we mortal beings, so statistical models are the best we've got - and they are plenty good enough as long as we understand their uses and limitations.
P.S. Everything is a wave, de Broglie was pretty much right.
Greed is the root of all evil.
If you throw a tennisball behind you, then quantumtheory states that it can be eanywhere behind you, but it is when you turn around and look for it, then you can decide where it is?
To call this science, is stupid.
Hello, Everett, goodbye Copenhagen.
The mathematical equation are still used. What your itnerpret them as MW, copenhagen wave collapse , or angel on a pin is pretty much unfalsifiable. Among my colleague copenhagen is still the majorly used interpretation , just look at QM article they speak of measurement and collapse. Not other world or angel on a pin.
C. Sagan : A demon haunted world:
http://www.amazon.com/gp/product/0345409469/
visit randi.org
https://www.xkcd.com/955/
...you forget that I personally find the Many Worlds interpretation distasteful. Therefore it is false.
Assuming random numbers don't exist, the new argument falls apart.
"The peculiar rules of quantum theory meant that it could be both dead and alive, until the box was opened and the cat's state measured."
I think maybe why everyone is finding so many strange side effects with this thought experiment is that it is based on a premise that it is fundamentally flawed.
Unless you're a hooker, there is no such thing as being dead and alive at the same time. You are either dead or alive... measuring the situation simply tells you the state you are in, and have probably been in for a while.
FFS the linked article didn't mention the original paper, thank goodness they even mentioned the authors. After tracking down the authors publications, I have located the original paper on arxiv. It's interesting to read, and seems to lend more thought experiment evidence to the many world interpretation.
As a lay person with an engineering background, I find QM to be exceedingly weird. All our intuition stems from interaction with the classical (macroscopic) stuff around us. Trying to extend it to the quantum world is rather frustrating.
I recently took up an opportunity to attend a few lectures on introductory quantum mechanics, just to see if I can develop some intuitive understanding of quantum mechanics. My key takeaway (please correct me if I am wrong) was that in the quantum world, measuring a quantum state and interacting with a quantum state are the same thing and will almost always modify the state being measured.
There were a host of other concepts which were introduced but most of them appear to boil down to this essential difference.
Interesting. Reminds me of Gödel's incompleteness theorems: any consistent system of axioms contains statements that are unprovable within the system. Equally mindblowing in a way: the Gödel metric
"You must try to forget all you have learned. You must begin to dream." -- Sherwood Anderson
Exactly the same level of weirdness, but for people who didn't get it previously and thought they did.
https://motls.blogspot.com/2018/04/frauchiger-renner-trivial-to-see-that.html
I have read a lot of popular science and it often seems to gloss over a lot of issues. So I can't really comment till I've done some more reading.
But the cat in the box experiment drew me to some conclusions, and raised a lot of questions.
A summary of my thoughts (which can be thought to be completely wrong by those in the know, I am in my own belief box at the moment): follow.
For something to be as big as a cat described entirely by a quantum wave form, the box must be impenetrable to everything being emitted from inside. ie the box itself must undergo no measurable transformation what ever happens inside the box. This would have to include gravity as well if any quantum gravity theory would emit information depending on the result of the first nuclear breakdown.
So if two impenetrable boxes somehow become combined lets pick another word "entangled" then the wave form to a "wave form calculator" (not an observer yet) would now need to cover both internal states of the boxes.
And you are now back with the one box scenario (though in the case in the article there are now two observers).
However there always seems to be some confusion or glossing over what an observer actually is. It could be a particle or some people even seem to suggest that it needs a conciosuness, but I think that is a bit of a stretch. I consider an observer to be anything that is instantaneously interacting with an object described by a wave form from it's point of view, as soon as it does this it has become part of the wave form from another external observer. But it now has special knowledge of the internal state of the wave form. Effectively it has "climbed in the box".
On a cosmic scale this seems to indicate that the parts of the universe that are beyond where light can travel from by now (due to expansion of the universe) are in one massive wave form, Until a single photon leaks out to give information about a past state of the wave form. The wave form collapses and a new wave form is born.
If there really is a dispute about what is in the box after two observers have measured it, then there really is something weird going on, as it would have to mean that quantum entanglement is partially broken, which would then solve the a paradox as the two boxes would appear to have but never entirely entangled themselves.
No doubt the many worlds interpretation may say that the combined boxes are from two "different worlds" so that they can give inconsistent results when individually measured.
My 2 pence worth. But I know I am wrong about a lot of the details here.
name the real-world benefits of quantum theory. There's PLENTY of scientific theories with tons of real-world applications that have real effects on humanity, but quantum physics just 'aint' in that list - so you need to temper your enthusiasm for this mental masturbation. It's the sort of thing one off the most useless branches of academia (theoretical physics) gets all excited by, but it sure is NOT one of the "most successful theories of the physical universe".
The Schrodinger's Cat thought experiment was a tool Schrodinger used in an argument, but it was never really that good for anything else (it was not of equal value to an Einstein thought experiment)... after all the superpositional state of the particle did not really matter to the cat - what mattered was the real-world effects of the particle and since the real-world effects posited in the experiment are NOT quantum states themselves, there's no real situation in which the cat both dead and alive, there's just the ignorance of the observer about the cat's condition before he opens the box to check (the cat is at any moment actually alive or dead and NEVER both), not that it matters because the entire field is on par with a beer-fuelled college bull session.
Bonus points to the person who just realized that the pop culture (and theoretical physics) fascination with Mr S's imaginary cat is completely misplaced and stupid.
It was never about the cat. It was never about a mystical cat-based situation. It was Schrodinger attacking a stupid argument with a silly example.
"could be both dead and alive"
Nope. Equal probability does NOT equal both states at the same time.
Yes, it would actually be quite delicious. ... few chunks of meat in there, some mushrooms, parsley add wine and lots of cream ... thicken with a light roux. Serve with fresh garlic bread and a glass of wine. ...
Reduce it to a quarter
Gotta go ... forgot I had an appointment at the animal shelter.
That's the reason she's asking that question.
Have you never learned to communicate on an emotional level? (Where the words don't matter, but only how you say things, and how it feels. It’s the main language of women and not that rare in men either [e.g. when they're angry].)
Or, if you don't love her, grow a spine, and leave. ... [the "dead" part] ... and you "love" her anyway, please get a therapy and leave her.)
(If she treats you like this
I don't understand what big problem people seem to have with this. You're a man. Act like one.
(I'm a man, by the way. But I don't act like "women can't be understood" or "men are dumb" so I can be lazy or trampled on.)
You are in a slave-master relationship. That you were told is marriage, but isn't. Just like your anticipatory subjection is not love, but makes you talk yourself into a fake feeling that compensates your fear.
A marriage is an equal relationship. That's your job just as much as hers.
Maybe you're just too afraid of being alone. I preferred being alone to being in what you call "marriage" though. It's the smaller pain.
Is this unique to the Copenhagen interpretation? Does the same problem exist in Bohmian mechanics?
What if the Physicist Farts in There?
Comment removed based on user account deletion
it could be both dead and alive, until the box was opened and the cat's state measured. Now, two physicists have devised a modern version of the paradox by replacing the cat with a physicist doing experiments -- with shocking implications.
So now there is a living and dead physicist doing experiments inside the box? Are they trying to create zombie science?
If i understand the paper correctly, then the gedankenexperiment could be interpreted as a "double slit (#include "obviousjokes.h") experiment with scientists".
In the double slit experiment a particle (e.g. photon, electron) is aimed through a plate with two slits (a,b) at a screen. after repeating the experiment many times one will see an interference pattern. Notably some regions of the screen stay blank, according to quantum theory (QT) no particles can end up there.
The way QT works we need to consider the paths of the particle through both of the slits (i.e. path A, path B), behind the plate there is interference between those two possibilities which determines the probability that a particle ends up on a spot of the screen (including probability zero in some region). The interference breaks down once one determines (measures) which of the slits (either a or b) the particle has passed. In that case there will be no interference pattern and the particle may end up in one of the spots the interference pattern leaves blank.
There are different "interpretations", what it is that "interferes", in the many worlds interpretation the particle took path A in one world and path B in another, and both worlds interacted to produce the interference pattern. The moment a scientist measures if the particle went through a or b he is in one of the worlds, the other world is excluded and can no longer make interference. Important is, that for the interference to happen the particles must be "isolated" in the sense that nothing happened that could distinguish between path A and path B.
Now instead of a particle they made the gedankenexperiment with scientists complete with a laboratory instead of the particles. The "double slit" becomes a measurement in which the scientist in an isolated laboratory is given a specially prepared quantum state S from which he can measure either result a or result b, instead of the paths there are now two "stories", either A or B to unfold, depending on the measurement. An outside observer then measures not A or B, but superposition states |A>+|B> or |A>-|B> (not normalized). These states are "orthogonal", only one or the other can result, like |a> and |b> are orthogonal, the first scientist can only have one measurement result.
The superposition state is similar to the measurement at the screen of the double slit experiment. It is designed so, that a measurement deciding between |A> and |B> is incompatible with a measurement deciding between A>+|B> and |A>-|B>. If one knows which path was taken (A or B) the interference between both possibilities is destroyed.
Now the first scientist is given a specially prepared quantum state: S=|a>+|b>. After his measurement an outside observer that is isolated from the measurement result will assume for the isolated laboratory the state |a,A>+|b,B>. So the outside observer will always get the result |A>+|B>, never |A>-|B> if the isolated scientist is given this state. The |A>-|B> result is like the blank spot on the screen.
The experiment is extended", by making the quantum state S dependent on a measurement of another scientist in another isolated laboratory. While it makes the story more complicated it is all based on the incompatibility of measuring either in the {|A>,|B>} space or the {|A>+|B>, |A>-|B>} space. QT says you can only get the result of one of those measurements, knowing if |A> or |B> was measured destroys the interference, after that measuring {|A>+|B>, |A>-|B>} is no longer determined by the state S the first scientist started with but on his result. Like in the double slit experiment the interference pattern is destroyed once it has been determined if path |A> or path |B> was taken.
Going from double slit to this gedankenexperiment the paths A or B the particle could take are now replaced by stories A and B about the measurement the scientist did.
If QT applies to the macroscopic syste
"By the way if anyone here is in advertising or marketing... kill yourself." -- Bill Hicks
Technically in quantum physics there are no boundaries.
Sounds a bit like a cartoon character questioning the existence of the cartoonist!
Self-importance and self-indulgence is the root of ALL evil.
You shoulda got an art degree instead of wasting time your time with chink lies & madeup "science".
Physicists both proved and disproved Quantum Mechanics. The author's heads promptly exploded after the paper was written.
When the Nature Communications publisher accepted the paper, their head exploded.
Scientific readers and peers, having accepted the paper's faultless QM logic, also blew their tops.
The Nobel committee, having decided to award the Nobel Prize to the (now headless) authors, immediately popped their caps.
Science journalists, interpreted and published the result, and fell over headless.
Readers worldwide saw those stories, thought, "Oh, I hadn't thought about that", and promptly exploded.
The illiterate and uninterested saw the commotion, thought, "hey, that looks exciting, wait for me!", and blew their heads off.
And that was that. Humanity, finally understanding the illogical and absurd Universe they lived in, ended.
the idea of applying quantum theory to understanding some characteristic of a thing, with the act of using quantum theory in the creation of the thing.
The transistor was not created based upon quantum mechanics, and even quantum tunneling in more recent semiconductors was not so much designed by theoretical physicists telling people how to make a new thing as it was a case of physics explaining an observed and used thing.
Some say this is a academic matter, but I say it still matters if the cart is in front of, or behind, the cart.